1. Field of the Invention
The present invention concerns an imaging tomography apparatus of the type having a first acquisition system with a first radiator and a first detector for generation of detector output signals that are a measure of the absorption of the radiation emanating from the first radiator and passing through a measurement region, and a second acquisition system with a second radiator and a second detector for generation of detector output signals that are a measure for the absorption of the radiation emanating from the second radiator, wherein, in the azimuthal direction, the first acquisition system is disposed at a first system angle and the second acquisition system is disposed at a second system, angle such that they can rotate around a common rotational axis. The invention moreover concerns a method for such a tomography apparatus for determination of the system angle of both acquisition systems.
2. Description of the Prior Art
Other tomography apparatuses with at least two acquisition systems are known from U.S. Pat. No. 4,991,190, German OS 29 51 222, German OS 29 16 848 and U.S. Pat. No. 6,421,412. The advantage of such tomography apparatuses with a number of acquisition systems compared to an apparatus with a single acquisition system is the possibility to examine a subject with an increased sampling speed or with an increased sampling resolution. A high sampling speed is of importance when movement artifacts that are caused by voluntary or involuntary movements of the subject (for example of an organ of an organism to be examined) must be minimized in the reconstructed image. In the examination (for example of a heart), for reconstruction of an artifact-free slice or volume image it is necessary that all exposures used for reconstruction optimally record the same movement state (phase) of the heart at the various rotational angle positions.
In addition to such single image acquisition, entire sequences of slice or volume images are also generated for representation of movement cycles for medical examinations. A higher sampling speed thereby offers the advantage of an improved temporal resolution of the imaged region affected by the movement cycle so that rapidly-changing movement states can be acquired.
A tomography apparatus with a number of acquisition systems can, however, be operated such that a higher sampling resolution is achieved in comparison to a tomography apparatus with only one acquisition system. This is particularly of importance when organs or organ parts of an organism must be resolved in a small examination volume, as in the case of examination of blood vessels, for example.
In a tomography apparatus with a number of acquisition systems, the acquired detector output signals of the various acquisition systems are combined with one another for reconstruction of a slice or volume image, both in the operating mode to increase the sampling speed and in the operating mode to increase the sampling resolution. The combining of the data ensues based on the knowledge of the system angles at which the acquisition systems are arranged in the azimuthal direction around the common rotational axis.